[Geysers] Hydrothermal Blast gets credit for Mary Bay

[Ron Keam]

If indeed this explosion was purely a hydrothermal eruption it would 
be the biggest I have heard about. However, I would like to say that 
the Rotomahana crater that formed during the 1886 "Tarawera" eruption 
in New Zealand on 10 June 1886 was approximately three kilometres in 
diameter.  The Rotomahana geothermal system that had existed there up 
till that date exploded as the result of intruding magma rising 
through it.  This initial explosion at the site of Rotomahana no 
doubt had a phreatic trigger, but the energy dissipated was almost 
exclusively hydrothermal in nature because the resulting base surge 
deposit has almost no basalt in it.  This event was the most 
energetic in the whole of the five to six hour eruptive sequence. 
Only one man who recorded his observations was in a position to see 
what was happening and he gave a brief but graphic account of the 
appearance of the discharge, illuminated as it was by the glow from 
the red-hot columns of basaltic lava simultaneously being ejected 
from the top of nearby Tarawera mountain and by the corruscating 
display of lightning accompanying it.  At the time no-one knew about 
base surges but it is quite clear that that was what he was 
describing.

Ron Keam

>This was in today's daily Oregonian's Science Section:
>http://www.oregonlive.com/science/oregonian/index.ssf?/base/science/120044311778980.xml&coll=7
>
>Pat Snyder
>_______________________________________________
>Geysers mailing list
>Geysers at lists.wallawalla.edu
>

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Ron Keam
The Physics Department
The University of Auckland
Private Bag 92-019
Auckland
New Zealand
Phone +64 9 373-7599 extension 87931
FAX +64 9 373-7445
EMail r.keam at auckland.ac.nz
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